Competition and coexistence in host-parasite systems: the myxomatosis case

APARICIO, JUAN PABLO; BONINO, N.; HERNAN GUSTAVO SOLARI

Population Ecology

elsevier

Año: 2004 vol. 46 p. 71 - 85

Abstract Co-circulation of several strains of parasiteshas been observed in many host-parasite systems.However, simple epidemiological models cannot sustainthis coexistence. In this work we study the coexistence ofviral strains in the myxomatosis case. Myxomatosis, ahighly lethal disease of the European rabbit, has beenused in Australia and Europe as a biological control ofrabbit populations. A few years after its introduction,the original highly virulent strains were almost completelyreplaced by field strains covering a wide range ofvirulence. Here, we study several mechanisms that mayexplain the field observations. First we considered spatialheterogeneity. The establishment of any strain overregions occupied by host populations may delay thespread of any superior competitive virus strain, producingglobal coexistence in the long term. On the otherhand, sub-populations with different resistance levels inepidemiological contact, as observed in the field, canmaintain several different virus strains co-circulating.The second class of mechanism introduces diversityamong hosts of a local population sharing a territory.We considered different classes of host resistance tomyxomatosis: belonging to a resistance class is a randomfact. Host age-dependent resistance is also especiallyconsidered. These types of population heterogeneity cansustain local coexistence for many years, althoughexclusion takes place for long enough periods. Theconcurrent action of both types of mechanisms couldexplain why the diversity of virus strains is sustained,and the local coexistence. Finally, we briefly discuss theinfluence of host genetic dynamics in the coevolution ofthe system.